The long-term goal of this work is to identify secretory protein biomarkers for lung adenocarcinoma diagnosis and prognosis in animals and in humans. In addition to gas exchange, the lung is an organ for host defense through inflammatory responses. Inflammation is a protective process that facilitates pathogen clearance and repairs tissue injury in the lung. However, exuberant inflammation can cause severe consequences and lead to carcinogenesis. One commonly induced pro-inflammatory gene group during pulmonary inflammation is the interleukin 6 (IL-6) family cytokines. Upon binding to their cell-surface receptors, IL-6 family members trigger activation (phosphorylation) of signal transducer and activator of transcription 3 (Stat3) by Janus-activated kinases (JAKs). To assess the consequences of STAT3 persistent activation in the lung, a doxycycline-controlled CCSP-rtTA/(tetO)7-CMV-Stat3C bitransgenic mouse model was generated recently in our laboratory that over-expresses STAT3C (the constitutively active form of STAT3) in alveolar type II (AT II) epithelial cells. In sequential steps, Stat3C over-expression promoted inflammation and adenocarcinoma in the lung with a high frequency (80%). This supports a concept that persistent inflammation triggered by the Stat3 signaling induces lung adenocarcinoma. In searching for human lung cancer samples, Stat3 up-regulation was highly associated with adenocarcinoma and squamous cell carcinoma. Therefore, Stat3 and its downstream genes can be used as biomarkers for lung cancer diagnosis in animals and humans. By Affymetrix GeneChip microarray analysis, multiple Stat3 downstream genes were identified in CCSP-rtTA/(tetO)7-CMV-Stat3C bitransgenic mice. A set of mostly-changed-genes from this list showed similar changes in human adenocarcinoma, confirming that Stat3 downstream genes are suitable for lung cancer diagnosis and prognosis. Since many Stat3 downstream genes are plasma proteins, we plan to use them for blood testing in both animal lung adenocarcinoma models and in human lung cancer patients. The central hypothesis for this proposal is that secreted protein products of Stat3 downstream genes can be used for diagnosis and prognosis of lung adenocarcinomas in animal models and in humans. Two aims are proposed to test the central hypothesis: 1) Characterization of Stat3 downstream genes as lung cancer biomarkers in animals. Three animal models that developed lung adenocarcinoma in association with inflammation will be used. Although they represent different molecular mechanisms for inducing lung adenocarcinoma, Stat3 gene up-regulation and activation are the common mechanism in all three animal models; 2) Characterization of Stat3 downstream genes as lung cancer biomarkers in humans. Putative secreted biomarkers will be screened in lung tissues and blood samples that are from human adenocarcinoma, squamous cell carcinoma and small cell lung cancer. After these studies, we would like to formulate a panel of protein biomarkers for diagnosis and prognosis in the blood of animal models and in human lung cancer patients.